1. Field of the Invention
The present invention relates to a coil for use in a charged particle deflecting electromagnet used in, for example, a synchrotron radiation generating apparatus, and a method of manufacturing such a coil.
2. Description of the Related Art
FIG. 12 is a schematic plan view of a charged particle generating apparatus disclosed in, for example, Japanese Patent Laid-Open No. 2300/1989. In the apparatus shown in FIG. 12, charged particles incident through an incident portion (not shown) and an acceleration portion (not shown) are deflected by two superconducting deflecting electromagnets 30 disposed in opposed relation and thereby move on an elliptical path 20.
FIG. 13A is a plan view of one example of a superconducting coil of the superconducting deflecting electromagnet 30 shown in FIG. 12, and FIG. 13B is a section taken along a line XIIIB--XIIIB of FIG. 13A.
Two superconducting coils 1, each of which is formed by winding a superconducting wire 2, are disposed in opposed relation at the upper and lower portion of the elliptical path 20. Each of the superconducting coils 1 is curved at a predetermined radius of curvature. The superconducting coil 1 has an inner diameter portion 1a located on the inner diameter side of the path 20, an outer diameter portion 1b located on the outer diameter side of the path 20 and curved in the same manner as the inner diameter portion 1a, and coil end portions 1c located between the inner and outer diameter portions 1a and 1b.
The thus-arranged superconducting coil 1 exhibits superconductivity when it is cooled to a temperature of, for example, -268.degree. C. Conduction of a current in the superconducting coil 1 exhibiting superconductivity produces a magnetic field having a high magnetic flux density of several teslas. The path 20 of the charged particles is bent in the manner shown in FIG. 12 by this generated magnetic field.
FIGS. 14A to 14C show another example of the conventional superconducting coil 1. This superconducting coil 1 has been described from page 2457 to page 2460 of IEEE TRANSACTIONS ON MAGNETICS, Vol. 1, Mag-24, No. 6, published in November 1985. FIG. 14A is a perspective view of the superconducting coil 1, FIG. 14B is a sectional view of the outer diameter portion 1b, taken along a line XIVB-XIVB of FIG. 14A, and FIG. 14C is a sectional view of the coil end portion 1c, taken along a line XIVC--XIVC of FIG. 14A.
In the superconducting coil 1 shown in FIG. 14, each of the coil end portions 1c is bent at a predetermined angle .theta. in a direction in which it is separated from the path 20 so as to allow the path 20 to be less affected by the magnetic field generated by the coil end portions 1c. This superconducting coil 1 is called the banana coil with bending ends. The superconducting coil 1 is disposed at the upper and lower portions of the path 20, as in the case of the coil shown in FIGS. 13A and 13B.
As shown in FIG. 14B, at the outer diameter portion 1b of the coil 1, N layers of the superconducting wire 2, from a first layer L1 to an Nth layer LN, are laid on top of another in the horizontal direction with the first layer L1 being disposed on the innermost side. At the inner diameter portion 1a, layers of superconducting wire 2 are formed similarly with the exception that the first layer L1 is disposed on the right end. At each of the coil end portions 1c, the layers of the superconducting wire 2 are laid on top of another in the vertical direction with the first layer L1 being disposed on the lowermost side.
A conventional method of manufacturing the superconducting coils 1 shown in FIG. 14A will be described below with reference to FIG. 15.
First, the first layer L1 of the coil 1 is formed by winding the superconducting wire 2 a predetermined number of times in a left-handed fashion (starting from the outer diameter portion 1b, the coil end portion 1c, the inner diameter portion 1a and then the coil end portion 1c) and outwardly (starting from the uppermost portion as viewed in FIG. 14B). Subsequently, the second layer L2 is formed by winding the superconducting wire 2 along the first layer L1 in a left-handed fashion and inwardly. Thereafter, the superconducting wire 2 is wound similarly along the previous layer until the number of layers reaches the predetermined number N to manufacture the superconducting coil 1.
In the conventional superconducting coil of the above-described type, since the superconducting wire 2 must be wound in a curved fashion and three-dimensionally, a complicated winding device (not shown) is required, increasing production cost and hence the price of the coil. Furthermore, the superconducting wire 2 is sequentially wound outwardly to form the odd layers and inwardly to form the even layers. At that time, particularly when the even layers are formed, a gap may be generated between the adjacent superconducting wires 2 at the portion indicated by an arrow R in FIG. 15. With the gap between the adjacent superconducting wires 2, when a current is supplied to the superconducting coil 1, the wire 2 may be moved due to the electromagnetic force, generating quenching which leads to breakage of the superconducting state. SUMMARY OF THE INVENTION
In view of the aforementioned problems of the conventional coils, an object of the present invention is to provide a method of manufacturing a coil for use in a charged particle deflecting electromagnet which can be manufactured without using a complicated winding device, which exhibits excellent characteristics and which is bent at two coil end portions.
To achieve the above object, the present invention provides a coil for use in a charged particle deflecting electromagnet in which a plurality of flat coil units are laid on top of one another, each of the flat coil units having two coil end portions which are bent such that they oppose each other, and in which the individual coil units are electrically connected with each other.
The present invention provides a method of manufacturing coils for use in charged particle deflecting electromagnets which comprises the steps of forming a plurality of flat coils, each of the flat coils being formed by winding a conducting wire a plurality of times, forming the coil units by bending the coil end portions of each of the flat coils such that they oppose each other, laying the coil units on top of another, and electrically connecting the coil units with each other.
In a preferred form, the coil manufacturing method comprises the steps of forming a plurality of two-layer flat coils by winding a conducting wire having a length corresponding to two layers from an intermediate portion thereof in two directions such that two ends of the conducting wire can be located at the outer diameter portion, forming the two-layer coil units by bending the two coil end portions of each of the two-layer flat coils such that they oppose each other, laying a predetermined number of two-layer coil units on top of another, and electrically connecting the two-layer coil units with each other.
In the coil for use in a deflecting electromagnet according to the present invention, since a flat coil formed by winding conducting wire outwardly is used, a gap between the conducting wires is small, and a shift of the conducting wires can be prevented.
In the coil formed by laying the two-layer coil units on top of another, since the number of connecting portions can be reduced and all the connecting portions are located on the outer side of the outer diameter portion, the influence of the magnetic field generated by the coil on the connecting portions can be alleviated.
When the connecting portions are extended from the coil, the influence of the magnetic field can be further alleviated.
In the method of manufacturing coils for use in deflecting electromagnets, since the coil unit is formed by bending the two coil end portions of a flat coil, a complicating winding device it not necessary.
A two-layer coil unit in which the connecting portions are located on the outer side of the outer diameter portion can be formed by winding a conducting wire outwardly from the intermediate portion thereof in two directions. Since winding of the conducting wire inwardly is not necessary, a gap between the conducting wires can be reduced. This prevents a shift of the conducting wires.
Other objects of the present invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference numerals designate corresponding parts in the views.